Yes, U.S. governors should be allowed to appoint people to vacant U.S. Senate seats, because it is less expensive than having someone go through an entire election just to be in office for a short period of time. It used to be that the legislature of each state appointed the Senators, so this is not a big break from tradition.
I think governors should be allowed to name appointees to vacant US senate seats primarily because holding an interim election takes time and money better spent for other things. The appointment is only temporary and would not have long-term consequences since an election will be held for the seat in good time. To sum up, allowing governors to make these appointments would save time and money. The direct will of the people will come into play during the next senatorial election.